1. Field of the Invention
The present invention relates to an exposure apparatus used for manufacturing semiconductor devices. More particularly, the present invention relates to a method of and a system for measuring stray light in an exposure apparatus.
2. Description of the Related Art
A variety of exposure apparatuses for transcribing a pattern on a wafer are used for manufacturing semiconductor devices. When using such an exposure apparatus, e.g., a photo scanner, flares caused by stray light when transcribing a reticle pattern on a wafer significantly affect performance of semiconductor devices made thereby. Therefore, it is important to minimize stray light in an exposure apparatus.
A widely used method for measuring stray light is the Kirk method. In the Kirk method, stray light is evaluated by measuring an exposure dose at which a predetermined size of an opaque pattern disappears due to the stray light.
This method allows short range stray light to be measured. Also, a light dispersion range can be obtained by measuring a variety of sizes of opaque patterns. However, in order to use opaque patterns for this purpose, a basic measurement with regard to a resist has to be made.
More particularly, after exposing a resist layer on a wafer to light filtered by the opaque pattern, the exposed resist layer on the wafer must be examined by an operator, e.g., using a microscope tester. Therefore, the process of obtaining measurement data is time consuming. Moreover, since a decision as to whether the reticle pattern should be transcribed or not depends is subjective, i.e., depends on the judgment of each individual operator, the decision could vary for the same measurement data. Therefore, accuracy and reliability of measured data are significantly affected by the operator.